Robin's pin cushion, also known as rose bedeguar gall, is an harmless growth caused by a species of gall wasp (Diplolepis rosae) it is part of the biodiversity roses support. The adult wasp lays eggs in the buds or developing leaves during mid-summer period. The eggs hatch into small white larvae that secrete chemicals that cause the abnormal growth.

Instead of buds developing into normal shoots and leaves, they are converted into hard woody structures that have an outer covering of moss-like leaves, which are either reddish pink or yellowish green. The internal part of the gall contains a number of chambers in which the grubs develop. The galls are fully developed during August and the insects overwinter inside the galls as pupae. During the autumn the outer covering of moss-like leaves tends to decay and this leaves the hard woody centre exposed.

This insect is more frequently found on wild roses or sucker growth but it does also occur on some of the rose species grown in gardens. The feeding activities of the gall wasp grubs do not have any real adverse effect on the rose, apart from creating the galls.